Typically, the amount of charge remaining in a battery used in electronics, such as a electronic still camera, a video camera, which uses a battery, such as various types of cells, as a power supply is normally grasped depending on the output voltage of the battery and is signaled to the user. When the battery is running down, battery replacement is typically urged. When the battery is extremely running down and battery voltage drops below a predetermined lower limit, the body of the camera is typically forced to be powered off to prohibit shooting.
According to an appreciated and thus applied system, recent electronic still cameras and video cameras are provided with an optical view finder plus a large-screen liquid crystal display monitor (LCD monitor) which is placed in an operating state as required by the user to display an image sensed picture or a reproduced image thereon.
However, the LCD monitor mounted to the camera and placed in an operating state as required, as described above is also supplied with power from the battery of the camera. Thus the load on the battery varies depending on whether the LCD monitor is in an operating state or a non-operating state. This load variation results in varied battery voltage and hence the following disadvantage.
More specifically, it is assumed that when the amount of charge remaining in the battery of the camera is detected with the LCD monitor operated and a decision is made that the battery voltage drops below the lower limit so that the camera is once powered off forcibly, i.e. when any more shooting is impossible without changing the battery and the user is thus urged to change the battery, the user again operates the power-supply button without changing the battery to place the power supply in an on state. In such case, since the LCD monitor is maintained in a non-operating state until the user operates an LCD display button for starting monitor display, the load on the battery is reduced by the power to be supplied to the LCD monitor as compared with the load on battery that was provided when the power supply was forcibly placed in the off state so that battery voltage increases and thus slightly exceeds the lower limit. Thus the power supply is not forcibly placed in an off state and this state is different from the previous state urging the user to change the battery. This confuses the user as to which decision is correct.
The present invention therefore contemplates a device detecting the amount of charge remaining in a battery, wherein a decision based on the detected amount of charge remaining therein with the LCD monitor operated that the battery should be changed is not reversed even when the LCD monitor is placed in an non-operating state and the load on the battery is thus reduced.